Fuel supply systems have been developed that have a fuel tank, a fuel manifold, fuel injector filling ports, and fuel injectors. As fuel is drawn from the fuel tank, it initially flows through a primary filter. The fuel then travels through the fuel manifold and is heated by the operation of the fuel injectors. Some of the fuel is injected into one or more cylinders and combusted, while the rest of the fuel may flow through a heat exchanger and return to the fuel tank. Some fuel supply systems contain a recirculation loop, wherein a high fuel flow rate is maintained in the recirculation loop, but a portion of the fuel exits the recirculation loop and flows through a heat exchanger and to the fuel tank. Ideally, functional and reliable fuel supply systems should have the following characteristics:                a fuel flow rate that is greater than a required minimum fuel flow rate through the fuel manifold;        a fuel pressure in the fuel manifold that is higher than a required minimum fuel pressure;        a fuel temperature, adjacent to the injector filling ports, that is lower than a maximum fuel temperature, which ensures reliable operation of the fuel injectors;        a low fuel pressure (ideally at atmospheric pressure) within the heat exchanger for minimizing the risk of fuel leakage from the heat exchanger;        a low fuel flow rate back to the fuel tank (ideally zero) for minimizing the addition of heat, from the fuel, to the fuel tank;        a low fuel flow rate from the fuel tank (ideally consumed fuel only) to minimize the debris carried from the tank, for extending the life of, for example, the primary fuel filter, and        a low fuel flow rate through, for example, the primary fuel filter for minimizing the risk of rupturing the primary fuel filter.        
Prior fuel supply systems without a recirculation loop fail to meet these design requirements simultaneously. In particular, prior fuel supply systems without a recirculation loop have had a high fuel flow rate back the fuel tank, and they have consequently had a high fuel flow rate from the tank and through the primary fuel filter. This unnecessarily shortens the lifespan of the primary fuel filter and puts the primary fuel filter at risk of having a ruptured filter element.
Likewise, Prior fuel supply systems having a recirculation loop have also failed to meet these design requirements simultaneously. For example, in such systems, if the return flow rate back to tank is too low, the heat exchanger in the return line is unable to remove sufficient heat from the fuel. In contrast, if the return flow rate back to tank is too high, then there will also be a high flow rate through the tank and the primary fuel filter. Again, this unnecessarily shortens the lifespan of the primary fuel filter and puts the primary fuel filter at risk of having a ruptured filter element.
Ultimately, what is needed in the art is a fuel supply system having as many of the aforementioned characteristics as possible.